The present invention is generally directed to panel fasteners and more particularly to a panel fastener joint, which joint includes a workpiece in the form of a section of sheet material and a fastener assembly; the workpiece and fastener assembly are constructed to confine the fastener assembly against axial and rotational movement thereby enabling ready use of the fastener assembly during subsequent assembly operations.
Panel fasteners for use in structural joints and connections are well-known in the art and are used extensively by the auto industry. For example, self-clinching fasteners are used in a number of applications wherein the fastener is assembled in a pre-punched hole in a section of sheet material, and then the head portion thereof is seated or embedded into the upper surface of the sheet material to cause displacement of a portion of the material radially inwardly of the aperture causing the material to co-flow into an annular locking groove formed in the fastener. The mechanical interlock thus created provides the means for maintaining the fastener in pre-assembled engagement with the sheet material so that subsequently a mating component can be attached thereto without the need for engaging the head portion with a tool or wrench. These fasteners, which are often referred to as "blind fasteners" are used for joints where ready access to one side of the workpiece is not available. An example of a self-clinching fastener of this type can be found in U.S. Pat. No. 3,967,669 which issued on July 6, 1976 and which is assigned to the assignee of the present invention. Another form of pre-assembled joint that is used is the type wherein the fastener assembly is disposed within a sheet material aperture and is welded thereto. Prior art joints of the type discussed have generally been found to be acceptable; however, they are costly and there has been a continuing need for reliable, less expensive assemblies.
The present invention provides a design wherein the fastener may be pre-assembled to a section of sheet material without regard for the thicknesses thereof. Also, as is well known, the structural integrity of a joint is, in large part, dependent upon the amount of material removed from the sheet material in forming the workpiece aperture. As more material is removed, the structural integrity of the resulting joint is diminished. With the present invention, the use of the multi-lobular aperture and cap end section serves to maintain a higher degree of integrity than achieved with prior designs. It is also necessary, when the fastener includes a threaded shank portion, to not only confine the fastener axially within the sheet material aperture, but to also prevent rotation upon subsequent assembly operations, wherein a mating threaded member is to be secured to the fastener.
It is therefore a general object of the present invention to provide a new and improved joint assembly.
It is a more particular object of the present invention to provide a joint assembly which includes workpiece sheet material and a fastener assembly which provides reliable fastener confinement within a sheet material aperture notwithstanding different sheet material thicknesses.
It is a further object of the present invention to provide such a joint assembly which exhibits improved structural integrity for the workpiece.
It is a still further object of the present invention to provide a fastener assembly for use in a joint including a workpiece in the form of a section of sheet material, and a fastener member having means for being confined within a sheet material aperture against axial and rotational movement and wherein the fastener is adapted to be engaged reliably with sheet material of different thicknesses.
The disclosed and hereinafter discussed embodiment of the present invention provides a fastener assembly for a joint with a workpiece of the type including a section of sheet material having an aperture (multi-lobular in the illustrated embodiment) having a center and defined by a periphery having a non-constant radial dimension from the center including a minimum radial dimension and a maximum radial dimension. The fastener assembly for the joint includes a fastener member having a head portion and a shank portion extending axially therefrom, the head portion including a first section having an outer peripheral dimension which is greater than the maximum dimension of the aperture, a second section extending axially from the first section towards the shank portion and having a non-constant peripheral radial dimension corresponding to the aperture dimension and receivable within said aperture, a third portion between the second section and the shank portion including a circumferential groove, and a resilient, contractable retaining ring carried within the circumferential groove. The shank portion and the head third section are dimensioned to pass through the aperture. The retaining ring has a free form dimension which enables it to be carried loosely within the circumferential groove, said free form dimension being such that the ring has a maximum dimension which is greater than the minimum dimension of said aperture, but less than the maximum dimension of said aperture. Said groove being of a depth such that the retaining ring may be contracted to an outer dimension less than the minimum dimension of the aperture, to permit said ring to be received through the aperture. After passing through the aperture, the ring may return to its free form dimension thereby retaining the fastener assembly in mounted relation with respect to the apertured section of sheet material. The corresponding peripheral dimensions of the aperture and the head second section co-act to prevent rotation of the fastener assembly within the aperture.